The disclosure of Japanese Patent Application No. 2001-394404 filed on Dec. 26, 2001, including the specification, drawings, and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an evaporative fuel adsorbing member disposed inside an air cleaner that is connected, for example, to an engine. The invention also relates to an air cleaner.
2. Description of the Related Art
The fact that regulations with regard to HC (hydrocarbons) that are discharged from a vehicle during stoppage thereof have been tightened in recent years causes a problem in that fuel remaining in an engine during stoppage of the vehicle and fuel that has leaked out from injectors are vaporized and leak out from a suction port of an intake pipe through an air cleaner.
Thus, as disclosed in Japanese Utility Model No. 62-35883 or the like, there has been devised an intake-system evaporative fuel adsorbing system in which an evaporative fuel adsorbing member such as a filter containing activated carbon is installed close to an intake duct, an air cleaner, or the like so as to prevent evaporative fuel from leaking out from a suction port.
In the aforementioned evaporative fuel adsorbing member, activated carbon for adsorbing evaporative fuel is homogeneously contained as a whole. Therefore, in order to capture a large amount of evaporative fuel, the evaporative fuel adsorbing member needs to be increased in thickness.
However, if the evaporative fuel adsorbing member is increased in thickness, the pressure loss in the entire intake system is increased. For this reason, the original performance of sucking air in the intake system may be reduced.
It is an object of the invention to provide an evaporative fuel adsorbing member and an air cleaner which are capable of efficiently adsorbing evaporative fuel and preventing a decline in the performance of sucking air by partially enhancing the performance of adsorbing evaporative fuel in a region containing a high concentration of evaporative fuel. It is another object of the invention to provide an evaporative fuel adsorbing member and an air cleaner which are capable of preventing adsorbent from deteriorating in purging efficiency.
A first aspect of the invention relates to an evaporative fuel adsorbing member that is disposed inside an air cleaner connected to an internal combustion engine and that has an adsorbent for adsorbing evaporative fuel that has flown backwards from the side of the internal combustion engine. This evaporative fuel adsorbing member comprises a first portion having a predetermined amount of the adsorbent, and a second portion having more than the predetermined amount of the adsorbent. In the first aspect, the evaporative fuel flows backwards into the second portion at a higher concentration than into the first portion.
It is to be noted herein that evaporative fuel is heavier than air and thus is not uniformly diffused. That is, when evaporative fuel flows backwards, the concentration of evaporative fuel (the concentration of HC) is high in a certain region inside the air cleaner, and the concentration of evaporative fuel (the concentration of HC) is low in another region inside the air cleaner. In other words, there are some differences in concentration of evaporative fuel inside the air cleaner.
Thus, as in the case of the first aspect, the adsorbent is disposed in the evaporative fuel adsorbing member such that the amount of the adsorbent contained in the evaporative fuel adsorbing member partially differs in accordance with the concentration of evaporative fuel flowing backwards. For example, a large amount of the adsorbent is disposed in a region into which a high concentration of evaporative fuel flows, and a small amount of the adsorbent is disposed in a region which contains a low concentration of evaporative fuel. In this manner, evaporative fuel can be efficiently adsorbed without excessively increasing the volume of the evaporative fuel adsorbing member. As a result, it is possible to prevent the pressure loss in a so-called intake system from increasing as a whole.
It is to be noted in the present specification that xe2x80x9cthe vertical directionxe2x80x9d means a direction in which gravity works, and that xe2x80x9cthe horizontal directionxe2x80x9d means a direction perpendicular to xe2x80x9cthe vertical directionxe2x80x9d.
It is also to be noted in the present specification that xe2x80x9cthe vertically lower portionxe2x80x9d of the evaporative fuel adsorbing member is located on the vertically lower side with respect to the center of the evaporative fuel adsorbing member, and that xe2x80x9cthe vertically upper portionxe2x80x9d of the evaporative fuel adsorbing member is located on the vertically upper side with respect to the center of the evaporative fuel adsorbing member.
It is also to be noted in the present specification that xe2x80x9cthe engine-side portionxe2x80x9d of the evaporative fuel adsorbing member is located on the side of the internal combustion engine with respect to the center of the evaporative fuel adsorbing member, and that xe2x80x9cthe non-engine portionxe2x80x9d of the evaporative fuel adsorbing member is located on the other side of the internal combustion engine with respect to the center of the evaporative fuel adsorbing member.
A second aspect of the invention relates to an evaporative fuel adsorbing member that is disposed inside an air cleaner connected to an internal combustion engine and that has an adsorbent for adsorbing evaporative fuel that has flown backwards from the side of the internal combustion engine. The evaporative fuel flowing backwards from the side of the internal combustion engine contains a plurality of kinds of components with different boiling points. To efficiently adsorb such evaporative fuel, the evaporative fuel adsorbing member has a plurality of kinds of the adsorbent with different pore diameters, and the plurality of kinds of the adsorbent with the different pore diameters are disposed in the evaporative fuel adsorbing member in accordance with ratios among the components contained in the evaporative fuel flowing backwards.
In general, high-boiling components of evaporative fuel tend to float along the bottom surface of an air cleaner.
Thus, according to the evaporative fuel adsorbing member of the second aspect, the evaporative fuel adsorbing member contains, for example, a plurality of kinds of the adsorbent with different pore diameters, and the adsorbent with a relatively large pore diameter is located on the side of the bottom surface of the air cleaner. Due to this construction, the high-boiling components of evaporative fuel can be efficiently adsorbed.